The invention relates to a part of a ski binding, especially a heel gripper, having a latch which is fulcrumed about at least one pivot axis disposed transversely of the length of the ski on a fulcrum piece which is affixed to the ski or is displaceable lengthwise of the ski against a biasing spring, and which in the gripping position overreaches a part of the ski boot, such as the heel or the like, or overreaches a part which can be bound to the boot, such as a sole plate, and having a thrusting mechanism whose thrust block, in the form of a piston-like part for example, is guided in or on the latch, on the side facing away from the boot, for displacement transversely of the pivot axis against the force of a thrust spring, and cooperates with a counter-thrust member fixedly provided on the fulcrum block such that, when the latch is rocked in the boot-releasing direction, the thrusting mechanism offers a resistance producing a return moment which increases within a resiliency range of the ski binding part, but vanishes as the latch rocks beyond the resiliency range.
Such bindings are known from German Petty Pat. No. 1,986,426, German Pat. No. 1,205,875 and German Pat. No. 1,578,761. According to German Petty Pat. No. 1,986,426, the latch is fulcrumed about a transverse axis on a cylindrical fulcrum head on the fulcrum block. The cylindrical fulcrum head has a wedge-shaped detent recess which cooperates with a springloaded, piston-like detent disposed in the latch, which has an apex adapted to the wedge shape of the detent recess and is guided for longitudinal displacement radially to the fulcrum axis in the latch. The ski binding part described in German Pat. No. 1,205,875 differs from the foregoing essentially only in that, for the fulcruming of the latch on the fulcrum block a cylindrical shaft fixedly joined therewith is provided, which has a lateral flat which cooperates as a counterthrust member with the flat face of a spring-loaded thrusting piston which in turn is disposed for displacement in the latch radially to the fulcrum axis.
In accordance with German Pat. No. 1,678,761, a spherical head is disposed on the fulcrum block, and on it the latch is fulcrumed. A conical detent recess is disposed in the spherical head and cooperates with a detent ball or detent piston having a conical point. The detent ball or detent piston are guided for displacement in the latch against the resistance of a detent spring and are disposed in the latch on the side thereof facing away from the ski boot. The arrangement is made such that the line of action of the detent ball or detent piston is at a radial distance above the center of the spherical head.
These known bindings, especially those described in German Petty Pat. No. 1,986,426 and in German Pat. No. 1,578,761, have a high internal friction within the resiliency range, since strong forces act on the detent members transversely of the direction of thrust of the detent members in the latches, so that the friction between the detent members and their guides increases greatly.
The result of the elevated internal friction is that, within the resiliency range, relatively high forces have to be transmitted by the boot to the latch in order to cause the latter to rock, while on the other hand, after the latch has rocked, the return forces exercised on the boot by the latch are comparatively low. Thus the binding returns to its precise clamping position only relatively slowly and, in the event of a plurality of successive shocks acting in the release direction, which of themselves are not dangerous for the skier, it may accidentally release.
In the binding in accordance with German Pat. No. 1,205,875, the friction resistance offered to the thrusting piston in the latch is somewhat lower, but on the other hand the binding is relatively soft in the area of its gripping position, since it takes a relatively great swing of the latch to produce an appreciable displacement of the thrusting piston.
Consequently it is the object of the invention to create a ski binding part corresponding to the kind described above, which within the resiliency range will be able to produce high return forces of the order of magnitude of the forces necessary for the release of the binding, while at the same time it is to be possible to produce a desired releasing characteristic.
This object is achieved by the fact that the longitudinal central axis in the direction of movement of the thrust block is at a radial distance from same below the fulcrum axis of the latch.
On the basis of this arrangement, when the latch is rocked away from its gripping position, relatively great amounts of the thrust block resistance that is to be overcome act directly in the direction of movement of the thrust block without exerting lateral forces on same tending to press the thrust block against its guides in the latch.
This brings it about advantageously that the forces which release the binding are determined essentially by the characteristics of the thruster spring as well as the configuration of the thrust block and counterthrust member, while the friction of the thrust block in the latch plays a comparatively unimportant part. At the same time, this assures a repeatable performance of the binding.
Great freedom can be exercised in the configuration of the thrust block and counterthrust member, so that any desired release characteristic is easily achieved.
For example, a lobe can be provided on the thrust block for cooperation with a cam surface provided on the fulcrum block as the counterthrust member against which the thrust block is biased by the thrust spring.
In a preferred embodiment of the invention, the lobe can be disposed below the longitudinal central axis of the thrust block.
It is also possible to cause a lobe-like cam follower on the fulcrum piece to cooperate with a cam surface on the thrust block.
In this case, in accordance with a preferred embodiment of the invention, the arrangement is made such that the cam surface provided on the thrust block engages the cam follower at a point that is below the central longitudinal axis of the thrust block when the ski binding part is in the gripping position.
The cam surface can desirably have two sections disposed one on either side of a crest, with their surface portions falling away from the fulcrum axis with increasing distance from the crest.
On the basis of this arrangement, the cam surface cooperates with the cam follower lobe such that the latch is forced back to its gripping position when one section cooperates with the follower lobe (resiliency range), while the latch is acted on in the opening direction when the other section engages the follower lobe.
Preferably, a portion of the fulcrum end of the thrust spring is to act as an abutment which cooperates with a part, such as the heel spur, on the latch and limits the tilt of the latch in the direction opposite the release direction. This measure prevents the latch from striking forcibly against the fulcrum piece when the latch is tripped to its gripping position after the ski boot has been removed from the binding. In this case the thrust spring serves as a correspondingly resilient abutment. An additional resilient buffer or the like thus becomes unnecessary.